Get the camera! A herd of woolly mammoths is thundering by! Within a few years, this conversation could be real. Using new technologies like the gene-editing system CRISPR, scientists are at work on projects to resurrect species like the woolly mammoth, which went extinct about 4,000 years ago. But is bringing them, or any extinct species, back a good idea? Here’s a look inside the debate.

Team "Bring it!"

Proponents of “de-extinction” include Harvard biologist George Church and Stewart Brand, founder of Revive & Restore, a private genetics start-up.

Scientists at Revive and Restore’s Woolly Mammoth Revival project are at work at figuring out how to modify Asian elephants to make them more like mammoths, until they essentially are mammoths. (There’s plenty of mammoth DNA available for them to use for reference, it has been preserved well in permafrost).

Believers in de-extinction think it may be able to transform ecosystems for the better. Mammoths, the theory goes, could be put to work grazing in the Arctic. Grazers are one key to transforming tundra back to its former glory as grasslands, which would help keep permafrost frozen and absorb more carbon, mitigating climate change.

Finally, de-extinction, like the biological equivalent of going to Mars, arguably will generate excitement and wonder at what science can do.

Team "Maybe not."

Ecologist Douglas McCauley is skeptical. He loves the idea of meeting a mammoth in real life. He’s just afraid de-extinction will turn species into curiousities, seen only in “zoo-like” contexts. If the mammoth does return, he said, “I want it doing its ecological thing in nature.”

However, the Arctic ecosystems where mammoths roamed have changed over millenia, McCauley said. Mammoths could become “ecological zombies,” like an invasive species, depleting resources and disrupting the environment.

Then there’s the cost: not just of bringing species back, but of caring for and managing the populations.

McCauley said it’s far more cost-effective to invest in protecting living endangered species, though they’re usually nowhere near as charismatic as the mammoth.

“I see a lot of value in using the same (de-extinction) technologies to helping species that are almost extinct.”